‘Unique ID’ Field Not Saving Settings

I’m trying to use the plugin to create a unique serial number on form submission. From within Gravity Forms, the ‘Unique ID’ field does not seem to be saving settings. I set the desired increment and starting serial, then click the Update button. But when I go back to the field settings everything is back to default. I tried this on my site and also from the demo site and modcoding.com (‘Settings not Saving?’ form) with the same failure. No changes to settings are saved after pressing the Update button.

Thanks for your help!